Whole Health: Sustainability's Back End

Supermarkets enjoy offering reusable bags, installing solar panels and other marketable sustainability initiatives. But if they're truly going to make an impact, retailers may need to get down and dirty. Wal-Mart and Tesco, two of the largest, most influential retailers on either side of the Atlantic, have been doing just that with new projects aimed at curbing emissions of a different kind cow gas.

Supermarkets enjoy offering reusable bags, installing solar panels and other marketable sustainability initiatives. But if they're truly going to make an impact, retailers may need to get down and dirty. Wal-Mart and Tesco, two of the largest, most influential retailers on either side of the Atlantic, have been doing just that with new projects aimed at curbing emissions of a different kind — cow gas.

At Wal-Mart's sustainability conference in Bentonville, Ark., this summer, the compa